Dear Konstantinos, Thank you for your quick response. As for the note in the documentation, I found it in this page http://getfem.org/userdoc/model_contact_friction_large_sliding.html <http://getfem.org/userdoc/model_contact_friction_large_sliding.html?highlight=large>. It reads "Sorry, for the moment the brick is not working". However, now that I double check it, it actually appears to be related to the nodal contact brick with projection, I may have thought it to be related somehow to large sliding bricks in general at some point.
Regarding the problem with contacts, I did use the example you provided as a baseline for my code. I tried new values for the augmentation parameter as you recommended and now I am obtaining better results. The solution appears to be highly sensible to this parameter since I get either penetration or unexpected deformation after relatively small changes. I'm still getting lots of these warning messages while solving Level 1 Warning in getfem_contact_and_friction_common.cc, line 47: Inverted element !-0.20579 Is there a way of getting rid of it or is this normal behavior? As a related question, is there a way for specifying the normals of the master surface? My meshes are highly irregular and I think it may also be a source of problems. Thank you very much for your help. Regards, Pablo On Tue, Apr 2, 2019 at 3:04 PM Konstantinos Poulios <[email protected]> wrote: > Dear Pablo, > > First of all I want to ask you about where you have read the statement > that the brick is not functional. This must be some old leftover that we > have to remove. The brick is in quite reasonable state and has been used to > produced many different results. > > The main trick for using the brick is the choice of the augmentation > parameter and the release distance. The augmentation parameter should be in > the order of the modulus of elasticity of the materials in contact (you can > try values from 1000 times smaller to 1000 times larger). Your choice about > the release distance sounds reasonable, maybe to be on the safe side you > could increase it to 10 times the element size instead of 3 time the > element size. > > Have you checked the corresponding included demo > > http://git.savannah.nongnu.org/gitweb/?p=getfem.git;a=blob;f=interface/tests/python/demo_large_sliding_contact.py > ? > > BR > Kostas > > On Tue, Apr 2, 2019 at 10:46 AM Pablo Arturo Alvarez Corrales < > [email protected]> wrote: > >> Dear getfem users, >> >> I've been trying to implement an elastostatic problem with contacts using >> the python wrapper for GetFEM v5.3. At first, I tried the contact bricks >> with non-matching meshes without any issues. However, since my problem >> considers large deformation, this approximation to contacts is not >> satisfying. >> >> I then tried the large sliding large deformation contact brick as >> following: >> >> md.add_filtered_fem_variable('lambda_n', mfu, CONTACT) >> contact_bid = md.add_integral_large_sliding_contact_brick_raytracing('r', >> release_dist) >> md.add_slave_contact_boundary_to_large_sliding_contact_brick(contact_bid, >> mim, CONTACT, 'u', 'lambda_n') >> md.add_master_contact_boundary_to_large_sliding_contact_brick(contact_bid, >> mim_c, CONTACT_C, 'u_c') >> >> where u, u_c, CONTACT and CONTACT_C represent the displacements and >> contact boundaries for the slave and master meshes respectively. >> >> Even though I get no errors at solving, the result appears to be >> incorrect. After deformation, penetration between slave and master meshes >> is significant, and changing the release distance for the raytracing >> transformation does not seem to help (here I used three times the mean >> element size). Also, I get a bunch of these in the console: >> >> Level 1 Warning in getfem_contact_and_friction_common.cc, line 47: >> Inverted element !-0.20579 >> >> I did read the note in the documentation saying that the brick is not >> working. However, it does not specify for which version so I wanted to be >> sure. >> >> Is this brick working properly and if not, is there any version of GetFEM >> in the repository that has one working version ? >> >> Thank you in advance, >> >> Pablo >> >> PD. Keep up the good work, this is an amazing library ! >> >
